As shown in FIG. 28, such a conventional sealing member is used for a separation preventive pipe joint 271 of a slip-on type. In the pipe joint 271, a spigot 275 formed on the end of a pipe 274 lies in a socket 273 formed on the end of a pipe 272 connected to the pipe 274.
A sealing member placement recess 276 is formed inside the socket 273 and contains a ring-shaped rubber sealing member 277. A lock ring groove 278 is formed behind the sealing member placement recess 276. A lock ring 279 is attached into the lock ring groove 278. An elastic member 280 for centering the lock ring 279 is disposed between the outer periphery of the lock ring 279 and the bottom of the lock ring groove 278. Moreover, a protrusion 281 is formed on the outer periphery of the end of the spigot 275 so as to be engaged with the lock ring 279 from the rear of the socket.
As shown in FIGS. 28 and 29, a fitting groove 282 is formed on an inner circumference 284 of the sealing member placement recess 276. The sealing member 277 includes a heel part 283 that is fit into and engaged with the fitting groove 282 and a bulb part 285 that is compressed between the inner circumference 284 and the outer circumference of the spigot 275 so as to generate a sealing surface pressure.
The bulb part 285 has first to third projections 286 to 288. The first projection 286 is formed on the outer circumference of the bulb part 285 so as to protrude outward in a radial direction A. The second projection 287 is formed on the socket rear end of the bulb part 285.
Moreover, the third projection 288 is formed on the inner circumference of the bulb part 285 so as to protrude inward in the radial direction A. The inside diameter of the third projection 288 is set to be smaller than the outside diameter of the spigot 275. Furthermore, a tapered part 289 is formed so as to gradually decrease in diameter from the inner circumference of the heel part 283 to the third projection 288.
With this configuration, as shown in FIG. 28, the heel part 283 is fit into the fitting groove 282 while the spigot 275 is inserted into the socket 273. This increases the diameter of the third projection 288 and holds the bulb part 285 between the inner circumference of the socket 273 and the outer circumference of the spigot 275. At this point, a clearance between the first projection 286 and the third projection 288 is compressed in the radial direction A.
The pipe joint 271 containing the sealing member 277 is described in, for example, Japanese Patent No. 4836870.
Another type of joint is, for example, a pipe joint 301 with a GX special pipe connecting cast-iron pipes as shown in FIG. 30. In the pipe joint 301, a spigot 305 formed on the end of a second pipe 304 is inserted into a socket 303 formed on the end of a first pipe 302 to be joined with the second pipe 304. A peripheral wall 306 radially protruding inward is formed all around the inner circumference of the rear part of the socket 303.
Moreover, from an opening end face 307 of the socket 303 to the peripheral wall 306, a sealing member insertion space 308 is formed between an outer circumference 305a of the spigot 305 and an inner circumference 303a of the socket 303 so as to surround the outer circumference 305a. An annular sealing member 309 for sealing between the outer circumference 305a of the spigot 305 and the inner circumference 303a of the socket 303 lies in the sealing member insertion space 308.
Furthermore, a lock ring groove 310 is formed behind the peripheral wall 306 so as to surround the spigot 305. The lock ring groove 310 is provided with a single lock ring 311 having one slit in its circumference. Moreover, a protrusion 312 is formed around the outer circumference of the end of the spigot 305 so as to be engaged with the lock ring 311 from the rear of the socket.
A pressing ring 313 is fit onto the spigot 305 and is opposed to the opening end face 307 of the socket 303 from the outside. The pressing ring 313 presses the sealing member 309 toward the rear of the socket 303. The pressing ring 313 is fastened to a flange 316 of the socket 303 with a plurality of T-head bolts 314 and nuts 315 and has a pressing face 317 in contact with the end of the sealing member 309 and a protrusion 318. The protrusion 318 that comes into contact with the opening end face 307 of the socket 303 keeps a distance A from the pressing face 317 to the opening end face 307 of the socket 303 at a predetermined distance.
With this configuration, when the pipes 302 and 304 are joined to each other, the lock ring 311 is first fit into the lock ring groove 310 and then the spigot 305 is inserted into the socket 303 until the protrusion 112 of the spigot 305 moves on the inner circumference of the lock ring 311 to the rear of the socket 303 with the sealing member 309 and the pressing ring 313 fit onto the spigot 305.
Subsequently, the sealing member 309 is inserted into the sealing member insertion space 308 from the opening end face 307 of the socket 303, and then the pressing ring 313 is fastened to the flange 316 of the socket 303 with the T-head bolts 314 and the nuts 315. At this point, the fastening of the nuts 315 moves the pressing ring 313 in a pressing direction B along a tube axis, allowing the pressing face 317 of the pressing ring 313 to press the sealing member 309 in the pressing direction B so as to press the sealing member 309 into the sealing member insertion space 308. After that, the protrusion 318 of the pressing ring 313 comes into contact with the opening end face 307 of the socket 303, preventing the pressing ring 313 from moving in the pressing direction B. At this point, the fastening of the nuts 315 is stopped to keep the distance A from the pressing face 317 of the pressing ring 313 to the opening end face 107 of the socket 303 at the predetermined distance. In this case, the rear end of the sealing member 309 does not reach the peripheral wall 306, forming a small space 320 between the rear end of the sealing member 309 and the peripheral wall 306.
When a region where the inner circumference 303a of the socket 303 and the outer circumference 305a of the spigot 305 are opposed in parallel to each other is defined as a compressed region C in the sealing member insertion space 308, the sealing member 309 is compressed in a radial direction D in the compressed region C. This keeps watertightness (sealing property) between the inner circumference 303a of the socket 303 and the outer circumference 305a of the spigot 305.
The pipe joint 301 including the pressing ring 313 is described in, for example, Japanese Patent Laid-Open No. 2010-286110.